One mechanical method of attaching auxiliary lenses is the ColorClip™ system. This system provides for holes drilled at various places around the outer perimeter of the auxiliary lenses. Soft plastic clips are then inserted into the holes. The jaw of the clip is an “S” shape. Removal and replacement of the auxiliary lenses is carried out by simultaneously (a) holding the primary frame; (b) positioning the auxiliary lens; and (c) gently bending back the “S” jaw of each clip. This is repeated for each of tie many (usually six) clips, and requires a significant degree of concentration and dexterity.
A similar system, ECLIPS, requires that the lenses be scored, coated with primer, and metal clips are then glued onto the auxiliary spectacles. The metal clips are bent such that they wrap around the primary spectacles. As repeated bending causes metal fatigue and failure, this system is not suitable for releasably securing auxiliary lenses to primary spectacles.
Another drawback of the ECLIPS and ColourClip™ systems is that each auxiliary lens must be separately attached to and removed from the primary frames. Unless the wearer goes to great lengths to accurately position each auxiliary lens, the auxiliary lens will often be positioned such that they are offset a few degrees axially in reference to the primary lens. Unless the auxiliary frames are perfectly circular, this offset makes the entire assembly, or worse, the wearer's face, appear bent or distorted.
Similarly, U.S. Pat. No. 6,007,197 to Locatelli teaches monocular auxiliary lenses having S-shaped clips for removing or replacing the auxiliary lenses. Each of the S clips on two lenses must be individually bent back in order to remove and replace the auxiliary lenses which thus can not be attached with a bridge.
Other mechanical methods for attaching auxiliary lenses are taught. U.S. Pat. No. 5,493,348 to Herald, Jr. et al. and U.S. Pat. No. 5,335,025 to Wang teach auxiliary lenses placed in thick auxiliary frames, which are configured with attachment means. These methods of attachment require thick frames that many wearers would find unsightly.
U.S. Pat. No. 5,438,378 to Blatter teaches an attachment member that is bulky and unsightly, particularly when viewed in profile.
U.S. Pat. No. 4,955,707 to Gazeley teach complex metal attachment means which are also unappealing in appearance. Also, the use of metal attachment means creates a risk that the lenses will be scratched while removing or replacing the auxiliary spectacles.
U.S. Pat. No. 5,907,384 to Kirsch et al. teaches a campanulate lens mounting strip having an arch-like bridge portion, with two hooks at the bridge, and one hook positioned near the bottom of the auxiliary frames. The utility of this apparatus is limited to reading glasses, and the auxiliary frames can only be attached to a primary frame specially configured for such attachment.
U.S. Pat. No. 5,867,244 to Martin and U.S. Pat. No. 5,696,571 to Spencer teach auxiliary spectacles which use tensioning. Complete auxiliary frames are required for these systems. If the auxiliary frame is bent significantly in any way, the method of attachment will fail. The tensioning clips are made from metal or a metal-like material. Thus, repeated bending will cause metal fatigue and failure. Also, the use of these clips requires that removal and replacement of the auxiliary spectacles be carried out at particular angles of engagement, which requires some dexterity and concentration.
U.S. Pat. Nos. 4,890,910 and 4,973,148, both to Gazeley, teach the use of a pair of rearwardly projecting flexibly resilient prongs on the auxiliary spectacles. The prongs are configured to sit in tensioning apparatus formed in the primary frame to effect a snap fit engagement. Removing and replacing the prongs requires a significant amount of force on the relatively weak bridges of the auxiliary and primary spectacles, and also requires awkward angles of engagement and disengagement. Thus this method is only useful in conjunction with thick, sturdy frames. Also, the prongs must be made of a metal or like material, thus creating a risk of damaging the primary spectacles, or worse, the wearer, when removing and replacing the auxiliary spectacles.
Thus, it would be desirable to have a simple and safe means for attaching auxiliary lenses to primary spectacles.